Fix spawner tests timeout on source builds (backport #1692)

[mergify]

As reported by @christophfroehlich in #1685, it seems that spawner tests are inconsistent and timing out after some time. I was able to reproduce it locally and upon checking it seems like the CM's internal mutexes are blcoking as there is no ControllerManagerRunner in some of these tests. Adding these should fix the above timeout issues. I've tested it locally and it seems to work

Fixes #1685

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This is an automatic backport of pull request #1692 done by Mergify.

[mergify]

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	both modified:   controller_manager/test/test_spawner_unspawner.cpp

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.31%. Comparing base (9eb64ad) to head (0db5940).

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1697      +/-   ##
==========================================
+ Coverage   62.30%   62.31%   +0.01%     
==========================================
  Files         105      105              
  Lines       11314    11318       +4     
  Branches     7925     7929       +4     
==========================================
+ Hits         7049     7053       +4     
  Misses        806      806              
  Partials     3459     3459              

Flag	Coverage Δ
unittests	62.31% <100.00%> (+0.01%)	⬆️

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Files	Coverage Δ
controller_manager/test/test_spawner_unspawner.cpp	59.01% <100.00%> (+0.54%)	⬆️